(a) Field of the Invention
The present invention relates to a flat panel display device, and in particular, to a flat panel display device which has a grid electrode with minimized distortion and alignment error.
(b) Description of Related Art
A flat panel display device includes an electron emission device which is a vacuum vessel with first and second substrates, electron emission sources provided at the first substrate and phosphor layers provided at the second substrate. Electrons are emitted from the electron emission sources to excite the phosphor layers. With the electron emission device, either hot cathodes or cold cathodes may be used as the electron emission sources. Among the cold cathode electron emission devices are field emitter array (FEA) types, surface conduction electron-emitter (SCE) types, and metal-insulator-metal (MIM) types.
In a typical electron emission device, a rear substrate with the electron emission source and driving electrodes, and a front substrate with an accelerating electrode (or anode electrode) and phosphor layers are sealed to one another by a frit seal to form a vacuum vessel. A plurality of spacers are typically mounted within the vacuum vessel to space the front and the rear substrates apart from each other by a predetermined distance.
A metal mesh type grid electrode with a plurality of apertures is placed between the front and the rear substrates. The grid electrode focuses the electrons emitted from the electron emission sources to enhance the color purity of the display screen, and heightens the voltage resistance characteristics between the driving electrodes on the rear substrate and the anode electrode.
The metal-based grid electrode has a thermal expansion coefficient that is very different from the glass-based front and rear substrates. Consequently, during the thermal treatment process, such as sealing, the grid electrode is easily distorted or misaligned due to the thermal stress applied to the grid electrode.
The alignment error of the grid electrode results in deteriorated display characteristics. That is, the electrons emitted from the electron emission sources do not pass through the relevant pixel apertures, but collide against the grid electrode and scatter, or pass through the incorrect pixel apertures, and land on the phosphor layers at the incorrect pixels. Furthermore, the distortion of the grid electrode can sometimes result in contact between the grid electrode and the electron emission sources, thereby causing an electrical short circuit.
Moreover, as the grid terminal for applying electrical signals to the grid electrode is often connected to the grid electrode by a simple band or a wire while being sealed thereto by a sealant, the grid terminal tends to be restrained against thermal expansion and contraction which can worsen the alignment error.